Ethyl lactate and other lactate esters are environmentally benign, non-toxic solvents derived from renewable carbohydrates via fermentation and separation processes. Ethyl lactate, for example, has very good solvent properties and a characteristic odor. Lactate esters can also be blended with fatty acid esters and other ester containing solvents to provide biosolvent blends with enhanced solvating, cleaning and penetration properties. For example U.S. Pat. No. 6,096,699 and No. 6,191,087 teach that lactate esters such as ethyl lactate blended with fatty acid esters such as methyl esters of soy oil fatty acids can be used for a variety of solvent cleaning, metal degreasing, paint and varnish removal applications. In another recent U.S. Pat. No. 6,797,684 B2, teaches that blends of lactate esters and d-limonene, a biobased solvent that is derived from citrus fruits have improved cleaning and solvent properties.
Lactate esters can emit an odor whose perception and tolerance can inhibit commercial acceptance of products containing them. Even in the blended solvents that are in the above-mentioned patents and other formulated products that have high concentrations of lactate esters, this odor perception and tolerance is difficult to overcome.
Another recent U.S. Pat. No. 6,890,893 B2, teaches a low odor composition for lactate esters and other ester biosolvents. This patent was based on the unexpected discovery that addition of small amounts of certain tertiary amines to lactate esters or ester solvent blends enhances the odor tolerance and reduces or eliminates the lingering bite/irritation sensation that appears after long or continuous exposure to these solvents. However, these amines have their characteristic ammonia like odor that is not desired in many general solvent applications. Furthermore, these amines may be reactive with various ingredients or components in solvent formulations. Furthermore, these amines are not really solvents and do not contribute to the solvating, drying or other properties that are required. Thus, even though the odor and tolerance properties were improved, other drawbacks that are described above limited their widespread use.
Aliphatic alcohols, either linear or branched, such as ethanol, iso-propanol, n-butanol, iso-butanol, n-pentanol or hexanol are some large volume chemicals that are widely used as solvents, reactants and as components of many formulations. Some of these alcohols, particularly ethanol, are now being made from renewable resources such as sugar cane, corn and other carbohydrate sources, in very large volumes as alternative liquid fuel for addition to gasoline.
In the past, n-butanol has also been made in very large quantities via fermentation of carbohydrates. Just recently, two major international energy and chemical companies, BP and Dupont, announced joint development and commercialization of ‘Biobutanol’ that will be derived from renewable carbohydrates, and will be used as an enhanced alternative fuel with ethanol, for blending into gasoline. Thus, some of the major alcohols are currently or soon becoming biobased products derived from renewable resources.
From the viewpoint of solvents, these alcohols lack some of the desirable properties namely, high solvency for a wide variety of polymers, too rapid drying rates particularly for ethanol, iso-propanol and n-butanol, low flash points and other properties. Lactate esters that have good solvating properties as well as low drying rates and high flash point can be considered as good blend solvents to improve the alcohols' solvent properties. It has now been discovered that blending lactate esters with the alcohols not only enhances the alcohols' solvent properties but also overcomes the odor and tolerance problems associated with the lactate esters. This result enables more widespread use of the solvent blends and growth of biobased solvents from renewable resources to replace petrochemically derived solvents.